Stephen McLaughlin's goal and a superb defensive performance saw Mansfield into the League Two play-off final with a 3-1 aggregate win over Northampton.
McLaughlin struck the only goal of the second leg, with Mansfield leading 2-1 from Saturday's opening game at Field Mill, on the half-hour mark after a perfect square ball from the returning Elliott Hewitt.
The Stags' goal owed a lot to referee Ben Toner's decision to wave play on when an offside Stephen Quinn made to run for the ball in the build-up, only to pull away with his arms raised just before Hewitt took over.
In the end, that strike was just the icing on the cake for Nigel Clough's side, who rode out heavy Northampton pressure with the hosts' only shot on target coming in the opening minute.
The beaten hosts may have felt aggrieved that what appeared two clear red cards, a late lunge from Kieran Wallace and an elbow from Stephen Quinn went unpunished, but the Cobblers could have little argument that the quality of Mansfield's performance saw them worthy winners to set up a Wembley date on May 28.
Stags stand firm to set up Wembley date
Mansfield came into their play-off semi-final second leg having lost all but one of their away games at top-nine opposition, conceding at least two goals five times and keeping only a solitary clean sheet, in a 0-0 at Bristol Rovers in February.
Inside the first minute of their latest trip to Northampton, who had beaten them 2-0 in October, they looked like wilting again when Josh Eppiah's header from Sam Hoskin's cross needed a fingertip save from Nathan Bishop to stop the hosts pulling level.
That early warning sign apart, they frustrated the home side throughout the 90 minutes and left them regretful that Hoskins blazing over a loose ball from a long throw-in would prove their only other clear-cut opportunity over 90 minutes.
This was a Mansfield side who had kept only six clean sheets in their 23 away league games this season, and just one in their last six, but screened by man of the match John-Joe O'Toole and Kieran Wallace, and with a colossal defensive showing inside his own box from Oliver Hawkins, they stood strong to reach the final with relative ease.
"From the first leg, in the first half you saw glimpses of what Clough is trying to create at Mansfield, how they pass the ball, their movement and creativity," former Mansfield manager Keith Curle told Sky Sports after full-time.
"But today you saw another side to Mansfield - nullifying the opposition. Players understanding their roles and doing their jobs. When you set up a team to be defensive, your wide players are vitally important, and they did that very well today."
Brady refuses to lay blame with officials
In addition to the two red card decisions which went against them Northampton were denied strong penalty shouts in either half.
Fraser Horsfall appeared to be bundled over by O'Toole in the area moments before Hoskins' first-half miss, before the same player left Louis Appere on the floor within minutes of the restart with Toner again unmoved.
Northampton manager Brady refused to use the decisions as a factor in his side's loss, instead focusing on the positives of their season, in which they missed out on the league title by four points and were pipped to automatic promotion by Bristol Rovers on the final day on goals scored.
"It's tough to take," he told Sky Sports. "I thought we played well, a few decisions didn't go our way, but it's been a fantastic season. 80 points, 23 wins, just missed out on automatic promotion by a whisker.
"The effort we gave tonight was incredible. This club is going the right way, the players pushed and pushed, there were a couple of penalty decisions which maybe should have been given but we can't cry about that. We've had to try to do it the hard way all season."
Opposite number Clough concentrated on his side's defensive performance, calling it and "outstanding effort" as they moved within one game of a first return to the third tier for 19 years.
"It was absolutely incredible," he told Sky Sports. "We sat in the dressing room here having lost 2-0 and gone joint bottom of the league, and we really were at rock bottom. To come here and experience a different feeling is lovely for them.
"We nicked the goal, and with the way we play we're always capable of doing that. But the defensive effort was incredible, the blocks we got in, the headers in our own box. Northampton were a kick away from getting automatic promotion - they're a very good team."
What's next?
Mansfield will keep their play-off dream alive at Wembley on May 28, live on Sky Sports Football; kick-off 4pm.